Approach light apparatus

ABSTRACT

Approach light apparatus for guiding an airplane to a runway having a plurality of discharge tubes each having a gutter type reflector for reflecting the light from the discharge tube at a large solid angle so that the light reflected by the gutter type reflector may be easily and positively seen by a pilot aboard an airplane making a landing, with the plurality of discharge tubes being located sequentially along a guiding line connected to the runway at a predetermined interval.

United States Patent Takauchi [4 1 Apr. 25, 1972 [54] APPROACH LIGHT APPARATUS 3,024,386 3/1962 Chauvineau ..3 15/24] S 2,328,413 8/1943 Bertram .....3l5/283 X [72] Imam Takauch" Japan 2,492,142 12/1949 Germeshausen. ..313/201 [73] Assignee: Masao Horlno, Tokyo, Japan 2,734,180 2/1956 Pennow ..240/1.2 X Filed. y 24 1969 3,237,003 2/1966 Tomkinson ..240/l03 X [21] Appl. No.: 844,327 Primary Examiner-Kathleen H. Claffy Assistant Examiner-David L. Stewart Foreign Application Priority Data Attorney-Hill, Sherman, Meroni, Gross & Simpson July 25, 1968 Japan ..44/52674 ABSTRACT Approach light apparatus for guiding an airplane to a runway [22] CCll having a plurality of discharge tubes each having a glmer type E g i H reflector for reflecting the light from the discharge tube at a 0 ea 3 5 large solid angle so that the light reflected by the gutter type reflector may be easily and positively seen by a pilot aboard an [56] References Cited airplane making a landing, with the plurality of discharge tubes being located sequentially along a guiding line con- UNITED STATES PATENTS nected to the runway at a predetermined interval.

2,938,149 5/1960 Wiley ..3 15/243 1 Claims, 9 Drawing Figures 2 /0 3 e1 4 (I 4 I 7 6 m Tr A 5 5 1;

VI I /2 3 IF "gig/2, 72 I2 I g PATENTED'APVR 25 I972 saw u or 4 lii. -fl

Q: mm tg fine APPROACH LIGHT APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge tube type approach light apparatus for guiding an airplane to a runway in an airportfor, making a safety landing. 21 Description of thePrior Art A conventional approach light apparatus for guiding an airplane to a runway has used a plurality of incandescent lamps each being provided with a parabolic reflector and which are aligned a predetermined distance along a guiding line continuous to the runway. If an airplane normally flys along and approaches the incandescentlamps to land, it can be automatically ledto the runway to make a safety landing. Danger has occurred in that the light from the incandescent lamps is often mistaken for the light from illumination lamps located along expressways or highways connected to the airport by the pilot aboard the airplane, which is dangerous because he may land off the runway.

I Inioifder to avoid such danger it has recently been proposed to ernployflash lamps such as xenondischargetubes located along the leading line connected to the runway in combination with the incandescent lamps, with each of the discharge tubes having a parabolic reflector. However, vwhenv an airplane makes a landing along a guiding line of a semi-circle to the runway of an airport, the pilot canonly see initial ones of the plurality of discharge tubes disposed alongthe semi-circular guiding line because the solid angle of the light emitted from each of the-discharge tubes with a parabolic reflector is relatively small. This is because the discharge is mounted at the focus of the reflector. The fact that the pilot can only see first few discharge tubes is very dangerous because of I the high speed of the airplane.

SUMMARY OF THE INVENTION The present invention provides novel lighting apparatus for guiding an aircraft wherein the total light generated is greatly improved .over those presently available. An inductance is mountedbetween a triggering electrode of a flash-type'light so that the luminous intensity increases at a slower rate than with normal flash lights andlasts'for a longertime such that the total light energy is substantially increased over flash lights of the prior art.

Also, a leakage transformer which is formed with a gap in its magnetic path is provided so as to improve the efficiency and lightdispersal of the flash unit.

The present invention provides a discharge tube type approach light apparatusfor an airplane which has a plurality of discharge tubes each having a specific reflector for increasing the solidangle of the light emitted therefrom.

The present invention also provides a discharge type approach light apparatus for an airplane including a plurality of, for example, xenon discharge tubes disposed along a semi-circular leading line continuous to a runway of an airport for an airplane to assure a safe landing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. Iv is a perspective ,view illustrating one example of a gutter type reflector according to the present invention;

FIG. 2 is a schematic diagram showing a runway and a straight guiding line connected thereto for an airplane provided with a plurality of approach light apparatuses disposed along the guiding line at predetermined intervals;

FIG. 3 is a schematic diagram showing a runway and a semicircular guiding line connected thereto with a plurality of approach light apparatuses mounted at predetermined intervals;

FIG. 4A is a graph showing the relationship between the luminous intensities of the approach light apparatus of the present invention and the prior art and positions in a horizontal plane; I

FIG. 4B is a graph showing the relationship between the luminous intensities of the approach light apparatus of the present invention and the prior art and positions in a vertical plane;

FIG. 5 is a schematic diagram illustrating one example of the present invention for actuating a xenon discharge tube;

FIG. 6 is a graph showing the relationship between the luminous intensities of the discharge tubes of the present invention and the prior art and the duration time of discharge of the discharge tubes; i

FIG. 7 is a schematic diagram illustrating another example of the present invention for actuating the discharge tube; and

FIG. 8 is a diagram used for explaining the schematic diagram shown in FIG 7. v I a v DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 reference numeral 1, designates a gutter type reflector member made of, for example, aluminum and reference numerals I and 1 show plate typereflector members made of alminum which are respectively'fixedto' both free ends of the gutter type reflector 1,. The inner surfaces of the reflector members 1,, I and I, arerespe'ctively formed to be mirrors by, for example, electrolytic polishing. The gutter type reflector member 1, and the plate type reflector members 1 and 1 form agutter type reflector l of'this'inventionLA line XX designates an axis of the gutter typereflector member 1, inits longitudinal direction and'the lines Y-Y respectively represent approximate symmetrical axes of the plate type reflector members 1 and l 'with each of the axes Y-Y beingparallelto one another and are approximately perpendicular to the axis XX. The cross-section of the gutter type reflector member I, on the plane perpendicular'to the axis XX and parallel to the plate type reflector members 1 and I is substantially a-parabola I Adischarge tube such, for example, a xenon discharge tube 6, the construction of which is well know to the art and the operating-electrical circuit for thetub e which will be explained later, is mounted along the focus line of the parabola of the guttertype'reflector member 1,. The part of the parabola 1,, above the axis X X is larger than that below the axis XX so that a' length W, between the axis Y-Y and the upper marginal edge of the reflector member I, is greater thanthe length W, between the axis Y-Y and the lower marginal edge 1, of the reflector memberl,.w w FIG. 2 is a schematic diagram-illustrating a runway Land a straight guiding line L connected to the runway L for guiding an airplane to the runway L in which a plurality of discharge tubes such as, for example, xenon discharge tubes, with each being provided with'the gutter type reflector l, are aligned with one another at predetermined intervals, such asat 30- meter spacings "along the guide line L. The discharge tube devices are disposed in such a manner that the axis XX is arranged substantially in the horizontal plane and perpendicular to the leading line L and such that the mirror surface of each reflector faces toward the direction along which an airplaneis guided to the runway L to make a landing. a

The angle of the light emitted from the discharge tube 6 and from the mirror surface of the reflector l of this invention is about 25 in the vertical planeand in aboutfl25 inv the' horizontal plane, which is shownin graphs of F IGSAA and4B v respectively. 7 v

In FIG. 4A the luminous intensity of the light emitted from the discharge tubes of the present invention and that of the light emitted from the conventional discharge tube in the horizontal plane are respectively shown. The line of the angle 0 corresponds toa line perpendicular to the longitudinal direction of the dischargetube substantially at thecenter point thereofjcorresponding to the line L in FIG. Zland the line of the angle corresponds to the line parallel to the longitudinal direction of the discharge tube. s

In FIG. 4A, curve b shows the' relationship of the luminous intensity and expanded angle of the device of the presentlin vention and curve b shows the response of a device of the prior art.

FIG. 4B shows the luminous intensity of the light emitted from the discharge tube of the device of the present invention and that of the light emitted from the conventional discharge tube in the vertical plane. Both are respectively shown with respect to the expanded angle of the light energy. The angle corresponds to the horizontal plane and the angle 90 to the vertical plane.

In FIG. 4B, curve b, designates the luminous intensity to the expanded angle of the light emitted from the discharge tube of the present invention and curve b, that of the prior art discharge tube.

As apparent from FIGS. 4A and 4B and also from FIG. 2, the light beam emitted from the discharge tube of the present invention is larger than that of the conventional discharge tube in both the horizontal and the vertical planes so that even if an airplane attempting a landing is displaced from the guid- I ing line L, the pilot can easily and positively find the approach light apparatus of the present invention, and can be returned to the guiding line L. As a result the airplane can be guided to the runway L to make a safe landing.

FIG. 3 is a schematic diagram which shows the runway L and a guiding line L" connected to the runway L for guiding an airplane to the runway L. The guiding line L issubstantially semi-circularly shaped and is provided with a plurality of the approach light apparatus according to the present invention which are disposed along the line L" at predetermined intervals.

If the guiding line is a semi-circular one as shown in FIG. 3 and the approach light apparatuses disposed along the semicircular leading line L" are conventional discharge tubes with each provided with a parabolic reflector, a pilot following along the guide line L" can only see the light emitted from the first few discharge tubes because the expanded angle of each of the conventional discharge tubes in the horizontal plane is only However, the airplane approaches the guide line L" at a high speed, and for the pilot to see only the first few lights is very dangerous.

In the present invention the expanded angle of the light emitted from each of the discharge tubes is about 120 in the horizontal plane and, the pilot can see many lights so that the pilot can positively guide the airplane to the runway L along the guide line L and make a safe landing.

FIG. 5 is a schematic diagram illustrating oneexample of an electrical circuit of this invention for actuating the discharge tube 6. In FIG. 5, reference numeral 3 represents an A.C. electric power source, reference character T, represents leakage transformers with primary windings [,which are respectively connected to the electric power source 3. Leakage transformers such as transformer T, are available on the commercial open market and such transformers are conventionally used in electric welders, for example. Such transformers are provided with a gap in the core of the transformer and when the current of the secondary of the leakage transformer abruptly increases, the flux is by-passed by the leakage circuit provided in the transformer and lowers the voltage of the secondary. 4, and 4 represent main rectifiers which have the inputs respectively connected to the secondary windings 1 of the transformers T Reference numerals 5, to 5,, inclusive, designate capacitors each having relatively large capacitance, for example, 65 microfarads (nF). The capacitor 5, is inserted between the common-output terminal 4,, of the main rectifiers 4, and 4 and the output terminal 4,, of the rectifier 4, through a diode D,. The capacitor 5 is mounted between the common output terminal 4,, and the output terminal 4,, through a diode D The capacitor 5, is mounted between the terminal 4,, and the output terminal4 of the rectifier 4 through a diode D and the capacitor 5, ismounted between the terminal 4,, and the terminal 4 through a diode D,. Reference numeral 7 designates an inductance coil, has one end connected to the common terminal 4,, and the other end to an anode 6,, of the discharge tube 6. Reference numerals 6, to 6,, inclusive, represent cathodes of the discharge tube 6. The cathode 6, is connected to the connection point of the capacitor 5, and the diode D,. Cathode 6, is connected to a point between the capacitor 5, and the diode D The cathodes 6, and 6, are connected to the connection point of the diode D and the capacitor 5;, and that of the diode D, and the capacitor 5, respectively. Reference numeral 8 represents a trigger electrode for initiating the operation of the discharge tube 6 and 10 a transformer for supplying high voltage trigger'pulses to the trigger electrode 8. A primary winding 10,, of the transformer 10 is connected between the connection point of the diode D, and the capacitor 5, and the connection point of the common output terminal 4,, and the inductance coil 7. Reference numeral 9 shows a silicon controlled rectifier element inserted between the first end of the primary winding 10,, of the transformer 10 and the connection point of the diode D, and the capacitor 5,. A gate 9, of the silicon controlled rectifier element 9 is connected to a timer 11 through a control circuit 12. The control circuit 12 consists of a transformer 12, a primary winding 12, of which is connected between one terminal of the power source 3 and the timer 11, a capacitor 12, connected across both ends of a secondary winding 12,, of the transformer 12,. Diodes 12 are inserted into the circuit and a capacitor 12, with the secondary winding 12,, for charging up capacitor 12 in a full wave rectifier manner. A diode 12, is inserted into the discharging circuit of the capacitor 12 for preventing a current frombeing supplied from the transformer 10 to the control circuit 12.

In the example shown in FIG. 5, when the circuit supplying the electric power from the power source 3 to the control circuit 12, namely the primary winding 12,, of the transformer 12, is closed by the timer ll, trigger current is applied to a gate 9, of the silicon controlled rectifier element 9 to make it conductive. As a result, the circuit of the primary winding 10,, of the high voltage transformer 10 is closed, whereby the A.C. electric power is supplied to the primary winding 10,. When the A.C. electric power is supplied to the primary winding 10,, of the transformer 10, a high voltage is induced in the secondary winding 10,, to supply high voltage to the trigger electrode 8. As a result, the discharge tube 6 emits light by discharge between the anode 6,, and the cathodes 6, to 6,.

FIG. 6 is a graph showing the relationship between the luminous intensity (the ordinate) of the light emitted from the discharge tube and the time (the abscissa) elapsed from the initiation of the flash or discharge. In the graph of FIG. 6 a curve crepresents the relationship of the discharge tube 6 actuated by the circuit shown in FIG. 5 and a curve C, shows the relationship of the prior art discharge tube.

As apparent from the graph in FIG. 6, the luminous intensity of the conventional discharge tube reaches its maximum value (about 6 X l0 ed) at the time 0.5 millisecond (m.s.) after the initiation of the flash and the duration of its flash is about 0.5 millisecond (m.s.). While, the luminous intensity of the discharge tube 6 of this invention reaches its maximum value (about 4.3 X 10 ed) at the time 0.6 millisecond (m.s.) after the initiation of the flash, and the duration time of its flash is about 1 millisecond (m.s.) or more. The maximum value of the luminous intensity of the discharge tube of this invention is smaller than that of the conventional one by a small amount but the duration time of its flash is longer than that of the conventional one. Further, the luminous intensity of the discharge tube of this invention gradually increases from the initiating time of the flash to the time when the luminous intensity reaches its maximum value and then gradually decreases from the maximum value to zero, which mean that the total light energy of the device of this invention is greater than that of the prior art.

As a result, the pilot can see the guide line easier and can positively fly the airplane to the runway to make a safe landmg.

FIG. 7 is another example of the discharge tube and the circuit for operating it according to the present invention. In this example reference character T, designates a leakage transformer and 3,, an A.C. electric power source supplying power to the leakage transformer T A secondary winding T of the leakage transformer T,, is connected to an input side of a rectifier 4,,. The output side of the rectifier is connected to the electrodes 6,, and 6 of a discharge tube such, for example, as a xenon discharge tube 6,,. Reference character 5,, represents a capacitor having a capacitance of, for example, 200 microfarads (,u.F) which is connected across the output side of the rectifier 4,,. Reference numeral 8,, is a trigger electrode which controls the discharge of the discharge tube 6 A block B designates a control circuit for applying high voltage to the trigger electrode 8,, at predetermined intervals. Since the control circuit B is similar to that of FIG. 5 in construction and operation, no detailed explanation will be given for this circuit.

The operation of the FIG. 7 example is explained in connection with FIG. 8. When the capacitor 5,, is charged by the A.C. power source 3,, through the leakage transformer T, and the rectifier 4,, as shown in a curve d in FIG. 8 and its voltage reaches a predetermined voltage A a voltage of about 5,0006,000 volts as shown in FIG. 8 by a curve e is applied to the trigger electrode 8,, at the times points T T T at these times the capacitor 5,, will be charged to the predetermined voltage A,. The results in the electrodes 6,, and 6,, of the discharge tube 6,, discharging the charge stored in the capacitor 5,, at the respective times T T T which generates light flashes. The time of the discharge is about 0.001 second. In the leakage transformer T,, there is provided a leakage magnetic path comprising a gap between a magnetic path formed in the primary coil T,,,, of the transformer T and a magnetic path formed in the secondary coil T so as to make the leakage reluctance great so that when the circuit including the secondary coil T, is short-circuited or the current flowing through this circuit is abruptly increased by the discharge of the discharge tube 6 the reluctance of the magnetic path in the secondary coil T is varied. As a result, the magnetic flux passes through the leakage magnetic path and the current in the primary winding T lowers the voltage across the secondary coil T,,,.

In FIG. 8, 1., l respectively represent times points when the discharging of the discharge tube 6,, has been entirely completed.

In the circuit of FIG. 7, only the discharge tube consumes electric power so that the power consumption is very small.

According to our experiences in the case of a conventional circuit in which a xenon discharge tube of 60 watts (W) and an ordinary transformer for operating the discharge tube are used, a series resistor of 500 ohms (Q)- 2 kilohms (k and a capacitor of 200 microfarads (uF) are required for operating the discharge tube. Further, when the discharge tube is flashed every second, the time constant of the capacitor and resistor is too great to increase the voltage build-up. Due to this fact when a voltage of 750 volts (V) is used as a electric power source for the transformer, the voltage across the capacitor is only increased to 5 50 to 600 volts.

According to the FIG. 7 example of this invention in which the leakage transformer T,, is employed instead of an ordinary transform and which dispenses with the series resistor, the voltage build-up rate across the capacitor 5,, is rapidly increased to make the voltage across the capacitor 5,, about 700 volts and power consumption is very small. This produces a very small amount of heat, so that electrical elements in or near the circuit are not subjected to high heat and their life span is increased.

I claim as my invention: 1. Approach light apparatus for guiding an airplane to a runway comprising:

a plurality of discharge tubes disposed along a guide line for said runway;

each of said plurality of discharge tubes having a pair of first discharge electrodes, a second discharge electrode disposed between said pair of first discharge electrodes and a trigger electrode and provided with a gutter type reflector and being located in front of said reflector along its focal line and substantially extending over its whole length in its longitudinal direction; an electric power source for supplying electric power to said discharge tubes;

a control circuit mounted between said electric power source and said trigger electrodes of said discharge tubes for controlling the discharge of said discharge tubes;

a leakage transformer connected to said electric power source;

a rectifier connected to said leakage transformer for rectifying its output;

at least two capacitors connected to said rectifier and respectively to said pair of first discharge electrodes and to said second discharge electrode for discharging electric charges received from said electric power source through said rectifier;

an inductance coil mounted between said rectifier and said second discharge electrode of said discharge tube for prolonging the discharge time of said discharge tube; and

said control circuit including a second transformer with its secondary connected to said trigger electrode, a silicon controlled rectifier connected in circuit with said rectifier and to the primary of said second transformer, and a timer connected between the gate of said silicon controlled rectifier and said electric power source to periodically gate said silicon controlled rectifier on and off. 

1. Approach light apparatus for guiding an airplane to a runway comprising: a plurality of discharge tubes disposed along a guide line for said runway; each of said plurality of discharge tubes having a pair of first discharge electrodes, a second discharge electrode disposed between said pair of first discharge electrodes and a trigger electrode and provided with a gutter type reflector and being located in front of said reflector along its focal line and substantially extending over its whole length in its longitudinal direction; an electric power source for supplying electric power to said discharge tubes; a control circuit mounted between said electric power source and said trigger electrodes of said discharge tubes for controlling the discharge of said discharge tubes; a leakage transformer connected to said electric power source; a rectifier connected to said leakage transformer for rectifying its output; at least two capacitors connected to said rectifier and respectively to said pair of first discharge electrodes and to said second discharge electrode for discharging electric charges received from said electric power source through said rectifier; an inductance coil mounted between said rectifier and said second discharge electrode of said discharge tube for prolonging the discharge time of said discharge tube; and said control circuit including a second transformer with its secondary connected to said trigger electrode, a silicon controlled rectifier connected in circuit with said rectifier and to the primary of said second transformer, and a timer connected between the gate of said silicon controlled rectifier and said electric power source to periodically gate said silicon controlled rectifier on and off. 